I just discovered a glitch which makes publishing changes impossible.

Steps to reproduce:

1. Make sure you have an account logged in, and you are NOT auto-confirmed (or confirmed).
2. Make sure you have "Prompt me when entering a blank edit summary (or the default undo summary)" option ticked. (This can be found under user preferences > Editing)
3. Make an edit which contains a new external link, leave the edit summary blank.
4. Because you are adding a new external link, the system requires you to do a captcha and submit again.
5. After resubmitting, you are prompted that you should resubmit your changes because your edit summary is blank.
6. After resubmitting, the system asks you to do the captcha again, going back to step 4. Your change is never published.

If the user's change does not involve any new external links, or the user's edit summary is not blank, everything is fine. Please look into this problem.

See also: T113700: one CAPTCHA (per action) should be enough to confirm humanity/ smart enough bot